Ovulation induction in rabbit does submitted to artificial insemination by adding lecirelin to the semen dose: preliminary results

The aim of this study was to analyze the effect of intravaginal administration of lecirelin on ovulation induction in rabbit does. Eighty pluriparous does (Martini genetic strain) were submitted to AI using a seminal dose of 0.5 ml containing about 10 million sperms. To stimulate ovulation, 4 homogeneous groups were submitted to different treatments: Control Group: 0.2 ml intramuscular administration of lecirelin (Dalmarelin, Fatro®); 0.2 Group: 0.2 ml intravaginal administration of lecirelin; 0.6 Group: 0.6 ml intravaginal administration of lecirelin; 2.0 Group: 2 ml intravaginal administration of lecirelin. In groups receiving an intra-vaginal administration, 25 µg/ml Dalmarelin was diluted in the seminal dose using benzilic alcohol (20 mg/ml) as excipient. Blood samples were collected from all females, to determine LH prior (-60, -30 and 0 minutes) and (30, 60, 90, 120 and 180 minutes) after AI, and progesterone once a week for 4 weeks. After 7 days from AI, 10 does per group were euthanized in order to analyze the ovarian status. The does of control group showed a high LH peak after 30 minutes from AI; whereas intra-vaginal administration of 0.2 and 0.6 ml determined a lower increase of LH blood concentration after 2 hours. The highest dose did not produce any LH or progesterone increase. The ovary status showed a higher number of corpora lutea in Control group (P<0.05), followed by 0.2 and 0.6 ones, whereas embryos were recorded only in Control and 0.2 groups. The unsuccessful of the other experimental groups could be ascribed to the negative effect of benzilic alcohol on seminal characteristic. Only 30% of 0.2 group does were pregnant and the prolificacy was 8 kits/doe. Compared to the control group, the progesterone concentration in pregnant does showed lower value in 0.2 group. In conclusion, in spite of the obtained results, it will be necessary to test different Dalmarelin formulations (lower volume, different excipient) to recommend the minimal dose to inject intravaginally for inducing ovulation.